<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>lesson 18</title>
  <script src="https://unpkg.com/vue@next"></script>
</head>

<body>
  <div id="root"></div>
</body>
<script>
  const app = Vue.createApp({
    data() {
      return { count: 1 }
    },
    template: `
      <counter v-model:ct="count" />
    `
  });
  app.component('counter', {
    props: ['ct'],
    methods: {
      handleClick() {
        this.$emit('update:ct', this.ct + 3); //修改count=this.ct+3
      }
    },
    template: `
      <div @click="handleClick">{{ct}}</div>
    `
  });

  const vm = app.mount('#root');
</script>

</html>